1. Field of the Invention
This invention relates to an abnormal condition signal transmitting device for a body of revolution such as a tire which transmits an aerial propagation signal to indicate the occurrence of an abnormal condition with the body of revolution. The invention, further, relates to a tire abnormal condition detecting device which detects the state of the hub nuts which secure a tire to the hub of the axle of a motor vehicle or the like. The invention, still more, relates to a tire abnormal condition alarming device for a motor vehicle which is provided with a remote control device including a signal receiver adapted to receive a door unlocking or locking aerial propagation signal from an operating key, in which a door locking mechanism is operated in response to the signal received by the signal receiver, to unlock or lock a door.
2. Related Art
One example of an abnormal condition signal transmitting device of this type is designed as follows: That is, the device is coupled to a tire. Upon detection of the abnormal condition of the tire, the device transmits an abnormal condition detection signal as an aerial propagation signal, and when a signal receiver receives the abnormal condition detection signa, informing means or the like is operated to inform the user of the occurrence of the abnormal condition. More specifically, the abnormal condition signal transmitting device coupled to the tire operates to detect the loosening of the hub nuts or the reduction of the air pressure of the tire, to output the abnormal condition detection signal.
The device is designed for instance as follows: Contact pieces are interposed between the tire wheel and the hub nuts adapted to fix the latter, thus forming abnormal condition detecting switches. When the hub nuts have been suitably fixed, the contact pieces are grounded through the wheel and the hub, and therefore the switches are held turned on. And when the hub nuts are loosened to electrically disconnect the contact pieces from the tire wheel, the switches are turned off. Furthermore, an air pressure sensor is coupled to the tire, and another abnormal condition detecting switch is provided which is turned off when the air pressure of the tire detected by the air pressure sensor is lower than a predetermined value.
When, in the abnormal condition signal transmitting device thus constructed, those abnormal condition detecting switches are turned off, transistors provided for the latter are turned on to provide abnormal condition detection signals, respectively.
The above-described conventional device suffers from the following difficulties: When the abnormal condition detecting switches detect the abnormal condition, the outputs of the switches change from ground level floating level to turn on the transistors. For this purpose, it is necessary to ground the circuit of the abnormal condition signal transmitting device. Accordingly, it is necessary to extend a grounding line from the device and to connect it to the part of the tire wheel which is at ground level. This line connecting operation is rather troublesome in coupling the device to the tire.
Furthermore, in order to control the on-off operations of the transistors in association with the detecting operations of the abnormal condition detecting switches, it is necessary to provide one transistor for each abnormal condition detecting switch, which increases the number of components as much.
Another example of the abnormal detection signal transmitting device of this type is installed as follows: When the tire wheel is fixedly secured, for instance, to the hub of the axle of a motor vehicle, the device together with the tire is fixed with the hub nuts. In this case, the device includes electrically conductive brackets, which are fixedly secured with the hub nuts so that the body of the device is electrically connected to the wheel, thus forming abnormal condition detecting switches. When any one of the hub nuts is loosened for some reason, the respective bracket is electrically disconnected from the wheel; that is, the abnormal condition detecting switch is turned off. When any one of the abnormal condition detecting switches is turned off, it is determined that an abnormal condition has occurred with the tire, and an abnormal condition detection signal is transmitted outside.
The above-described conventional device is disadvantageous in the following points: That is, four brackets extended from the body of the device are secured to the wheel by tightening the hub nuts. Even if one of the hub nuts is loosened, the brackets fixedly secured with the remaining hub nuts are held stable; that is, the bracket whose hub nut has been loosened is not immediately electrically disconnected from the wheel, and therefore the abnormal condition is not immediately detected.
Furthermore, another example of the device of this type operates to detect abnormal conditions; that is, the loosening of any one of the hub nuts which fixedly secure the tire to the hub, or a reduction of the air pressure of the tire, to inform the user of the abnormal conditions. In the device, sensors are interposed between the hub and the hub nuts fixing the tire, to detect the contact state therebetween, and an air pressure sensor is provided to detect the air pressure of the tire. Furthermore, a signal transmitter is mounted on the wheel, to transmit the detection signals of those sensors, and a signal receiver is mounted on the motor vehicle, to receive the detection signals, so that, when an abnormal condition occurs with the tire, an alarm unit is operated to inform the user of the occurrence of the abnormal condition.
With the device, the difficulty can be eliminated that the hub nuts come off to allow the tire to come off, and a reduction of the air pressure of the tire can be detected. Those effects contribute to improvement of the safe operation of the motor vehicle.
The abnormal conditions of the tire are for instance as follows: One example of the abnormal conditions relates to how sufficiently the tire has been secured with the hub nuts; that is, the abnormal condition is such that, while the vehicle is traveling, the hub nuts fixing the tire are loosened or come off. In another example, the tire air pressure is decreased. In another example, while the vehicle is being parked, or the user is away from the vehicle, the tire is stolen. Thus, various abnormal conditions occur with the tire as the case may be.
In the case where, when the vehicle is being parked, and is not accompanied by the user, the hub nuts are loosened or come off, there may be a possibility that the tire has been stolen. On the other hand, if, when the vehicle is traveling, the same abnormal condition occurs, then the tire may come off, which may results in a serious accident. Thus, when, in the case where the vehicle is not accompanied by the user, an abnormal condition is detected with the tire, it is necessary for the vehicle to perform a warning operation, for instance, to operate the horn or the like to sound a warning signal outside or inform the user of the occurrence of the abnormal condition by radio. If, in this case, the user is in the vehicle, instead of the horn producing loud sound, a buzzer or lamp should be used to inform the user of the occurrence of the abnormal condition.
However, the above-described conventional device is unable to perform the warning operation separately according to the above-described various situations, because the signal transmitter mounted on the tire wheel merely transmits a signal indicating the abnormal condition of the tire. That is, in the case where the device is so designed as to operate the horn to give a warning signal, the device is disadvantageous in that, when the user is in the vehicle, the sound produced is too loud for him to bear. On the other hand, in the case where the device is so designed as to operate the buzzer to give a waning signal, the device suffers from the difficulty that, for instance when the tire is stolen, it is impossible to inform the user of it who is outside the vehicle.